Based on the relationship between the three-dimensional structure of nitroheterocyclic compounds and their chemotherapeutic activity, it is proposed to design and evaluate compounds for potential antischistosomal activity. In conjunction with biochemical and physiological studies of the parasites, these investigations should provide information about the precise conformational requirements conferring antischistosomal activity, about the mechanisms by which these compounds exert their chemotherapeutic activity, and about the possibility of a rational development of more effective and less toxic antischistosomal and other anthelmintic agents.